Grazing-incidence Synchrotron Radiation Diffraction Research Articles

Grazing-incidence synchrotron radiation diffraction studies on irradiated Ce-doped and pristine Y-stabilized ZrO2 at the Rossendorf beamline.

In this work, Ce-doped yttria-stabilized zirconia (YSZ) and pure YSZ phases were subjected to irradiation with 14 MeV Au ions. Irradiation studies were performed to simulate long-term structural and microstructural damage due to self-irradiation in YSZ phases hosting alpha-active radioactive species. It was found that both the Ce-doped YSZ and the YSZ phases had a reasonable tolerance to irradiation at high ion fluences and the bulk crystallinity was well preserved. Nevertheless, local microstrain increased in all compounds under study after irradiation, with the Ce-doped phases being less affected than pure YSZ. Doping with cerium ions increased the microstructural stability of YSZ phases through a possible reduction in the mobility of oxygen atoms, which limits the formation of structural defects. Doping of YSZ with tetravalent actinide elements is expected to have a similar effect. Thus, YSZ phases are promising for the safe long-term storage of radioactive elements. Using synchrotron radiation diffraction, measurements of the thin irradiated layers of the Ce-YSZ and YSZ samples were performed in grazing incidence (GI) mode. A corresponding module for measurements in GI mode was developed at the Rossendorf Beamline and relevant technical details for sample alignment and data collection are also presented.

Microstructural, chemical and textural characterization of ZnO nanorods synthesized by aerosol assisted chemical vapor deposition

ZnO nanorods were synthesized by aerosol assisted chemical vapor deposition onto TiO2 covered borosilicate glass substrates. Deposition parameters were optimized and kept constant. Solely the effect of different nozzle velocities on the growth of ZnO nanorods was evaluated in order to develop a dense and uniform structure. The crystalline structure was characterized by conventional X-ray diffraction in grazing incidence and Bragg–Brentano configurations. In addition, two-dimensional grazing incidence synchrotron radiation diffraction was employed to determine the preferred growth direction of the nanorods. Morphology and growth characteristics analyzed by electron microscopy were correlated with diffraction outcomes. Chemical composition was established by X-ray photoelectron spectroscopy. X-ray diffraction results and X-ray photoelectron spectroscopy showed the presence of wurtzite ZnO and anatase TiO2 phases. Morphological changes noticed when the deposition velocity was lowered to the minimum, indicated the formation of relatively vertically oriented nanorods evenly distributed onto the TiO2 buffer film. By coupling two-dimensional X-ray diffraction and computational modeling with ANAELU it was proved that a successful texture determination was achieved and confirmed by scanning electron microscopy analysis. Texture analysis led to the conclusion of a preferred growth direction in [001] having a distribution width Ω=20°±2°.

Characterisation of phase relations and properties in air-oxidised Ti 3SiC 2

The oxidation of Ti 3SiC 2 in air from 25 to 1450 °C is characterised by differential thermal and gravimetric analysis (DTA/TGA), X-ray diffraction (XRD), grazing-incidence synchrotron radiation diffraction (GISRD), neutron diffraction (ND), transmission electron microscopy (TEM), secondary ions mass spectroscopy (SIMS) and Vickers indentation. The diffraction results show that rutile formed at a temperature of ∼750 °C. A glassy phase – formed at >1000 °C – devitrified upon cooling to room temperature to form tridymite but crystallised to cristobalite at temperatures ≥ 1300 °C. Composition depth-profiling of the surface layer oxides by XRD, GISRD and SIMS revealed a graded distribution of phases (TiO 2, SiO 2 and Ti 3SiC 2) both at the nanoscale (≤1100 °C) and microscale level (≥1200 °C), which is particularly distinct at the interfaces. The oxide layers also exhibit a graded variation in microhardness.

Mapping the structure, composition and mechanical properties of human teeth

The structure-property relationship in human adult and baby teeth was characterised by grazing-incidence synchrotron radiation diffraction, optical and atomic-force microscopy, in addition to Vickers indentation. Similarities and differences between both types of teeth have been highlighted and discussed. Depth-profiling results indicated the existence of contrasting but distinct gradual changes in crystal disorder, phase abundance, crystallite size and hardness within the baby and adult enamel, thus confirming the graded nature of human teeth. When compared to the adult tooth, the baby enamel is softer, more prone to fracture, but has larger hydroxyapatite grains. Vickers hardness of the enamel was load-dependent but load-independent in the dentine. The use of a “bonded-interface” technique revealed the nature and evolution of deformation-microfracture damage around and beneath Vickers contacts.

Mapping the Microstructure–Property Relationships in Cortical Bone

Structure-property relationships in bovine cortical bone have been characterised using grazing-incidence synchrotron radiation diffraction, Vickers indentation and mechanical testing. Depth profiling results indicated the existence of distinct gradual changes in crystal disorder, phase abundance, and texture of hydroxyapatite whilst the crystallite size was depth-independent.

Microstructure–Property Relationships in Human Adult and Baby Canine Teeth

Structure-property relationships in baby and adult teeth have been characterised using grazing-incidence synchrotron radiation diffraction and Vickers indentation. Similarities and differences between both types of teeth have been highlighted and discussed. Depth profiling results indicated the existence of contrasting but distinct gradual changes in crystal disorder, phase abundance, crystallite size and hardness within the baby and adult canine enamel, thus confirming the graded nature of human teeth. When compared to the adult tooth, the baby enamel is softer, more prone to fracture, but has larger hydroxyapatite grains.

Depth‐Profiling of Crystal Structure, Texture, and Microhardness in a Functionally Graded Tooth Enamel

The graded nature of crystal structure, texture, and microhardness of human enamel has been characterized by grazing‐incidence synchrotron radiation diffraction and Vickers indentation. Results show that the composition of tooth enamel consists mainly of calcium apatite or hydroxyapatite (HAP). The HAP crystals formed near the occlusal surface are aligned approximately orthogonal to each other between the axial and occlusal sections. In addition, the tooth enamel has been shown to be a hierarchical graded biomaterial with a distinct gradation in crystallinity, texture, crystallite size, and hardness, which is somewhat akin to that of the fibrous microstructures found in natural plants. A “graded‐interface” approach is proposed as a biomimetic model for designing new dental or restorative materials as well as for joining of dissimilar materials.

Depth profiling of phase composition in a novel Ti 3SiC 2–TiC system with graded interfaces

A high-temperature vacuum heat-treatment process has been used to design novel Ti 3SiC 2−TiC composites with graded interfaces. The phase evolution and the graded nature of this system have been characterised by X-ray diffraction (XRD) and grazing-incidence synchrotron radiation diffraction (GISRD). Results show that a TiC layer commenced to form near the surface of Ti 3SiC 2 at 1200 °C in vacuum and grew rapidly in thickness with temperature rising to 1500 °C. Depth profiling of the TiC layer by XRD and GISRD has revealed a distinct gradation in phase composition.

Depth-profiling of phase composition and preferred orientation in a graded alumina/mullite/aluminium-titanate hybrid using X-ray and synchrotron radiation diffraction

X-ray diffraction (XRD), grazing-incidence synchrotron radiation diffraction (GISRD) and multi-wavelength synchrotron radiation diffraction (MWSRD) have been successfully used for near-surface depth profiling of phase composition and texture in a functionally-graded alumina/mullite/aluminium-titanate hybrid prepared by an infiltration process. Depth profiling of near-surface information both in the nanometer and micrometer scale has been done by (a) varying the X-ray wavelength, (b) varying the grazing-incidence angle, and (c) gradual polishing of the sample surface with diamond lap. Results show a distinct gradation in the phase abundance near the surface of the hybrid sample. The distribution of mullite near the surface is highly textured and shows a distinct depth-dependent gradation in preferred grain-orientation. The unique but powerful capability of XRD, GISRD and MWSRD as complementary tools for depth profiling the near-surface region of graded materials has been demonstrated in this work.

Depth profiling of a functionally graded alumina/calcium-hexaluminate composite using grazing incidence synchrotron-radiation diffraction

Abstract Grazing incidence synchrotron radiation diffraction (GISRD) has been successfully used for near-surface depth profiling of phase composition, texture and residual strains in a functionally-graded alumina/calcium-hexaluminate (CA 6 ) composite prepared by infiltration process. Depth profiling of near surface information both in the nanometre and micrometre ranges have been done by using angles of incidence below and above the critical angle ( α c ) for total external reflection. The penetration depth increased to several hundred angstroms as α approached α c . Above α c there was a rapid increase in penetration depth to a thousand angstroms or more. As the penetration depth increased the intensity of CA 6 peaks relative to those of alumina became less intense, indicating a distinct gradation in the phase abundance. The distribution of CA 6 grains at the near-surface was highly textured and showed a distinct depth-dependent gradation in texture. The presence of graded residual strains in the composite due to thermal expansion mismatch between the phases has been computed and verified from the display of line shifts. The unique but powerful capability of GISRD as a complementary tool for depth profiling the near-surface information of graded materials has been demonstrated in this work.

Depth profiling of near-surface information in a functionally graded alumina/aluminium titanate composite using grazing-incidence synchrotron radiation diffraction

Grazing-incidence synchrotron radiation diffraction (GISRD) has been successfully used for near-surface depth profiling of phase composition in a functionally graded alumina (A)/aluminium titanate (AT) composite prepared by an infiltration process. Depth profiling of near-surface layers both within the nanometer and micrometer range could be done by using angles of incidence below and above the critical angle ( α c) for total external reflection. The penetration depth increased to several hundred angstroms as α approached α c. However, above α c there was a rapid increase in penetration depth to several thousand angstroms or more. As the penetration depth increased, the intensity of aluminium titanate peaks relative to those of alumina became less intense, indicating a graded change in the phase abundance. The presence of graded residual strains in the composite due to the thermal expansion mismatch between the phases has been computed and verified from the display of line shifts. The unique but powerful capability of GISRD as a tool for depth-profiling the near-surface information of graded materials has been demonstrated in this work.

Observation of Hexagonal Crystalline Diffraction from Growing Silicate Films

Clear evidence for hexagonal crystallinity in surfactant-templated silicate films growing at the air-water interface is presented for the first time. Grazing incidence synchrotron radiation diffraction shows the development of diffraction spots just as the induction phase, identified previously, is completed. The observed hexagonal diffraction represents the in-plane ordering of the first two-three layers of film formed at the interface.